The present invention relates generally to sanitizing compositions for controlling microbial growth in recirculating water systems, and more particularly to stable, high available halogen 1,3,5-triazine-2,4,6-trione compositions with a rapid dissolution rate.
Halogen compounds, particularly those with chlorine and bromine, have long been used as sanitizers to kill bacteria, fungi, and algae in recirculating water systems. These halogen sanitizing compounds are relatively low in cost and provide broad-spectrum control even at low (ppm) concentrations.
Sodium hypochlorite, lithium hypochlorite and calcium hypochlorite are among the most popular halogen sanitizing compounds, in part because they have high dissolution rates or disperse readily in water. This characteristic is beneficial when it is necessary to provide high halogen levels to recirculating water systems in a short period of time (often referred to as slug-feeding, shocking, or superchlorination).
Of the inorganic halogen sanitizing compounds, calcium hypochlorite, which contains 65% to 75% available halogen, is the most widely used dry granular material because of its low cost and high halogen content. Sodium hypochlorite and lithium hypochlorite, while capable sanitizing compounds, are less cost-effective and have lower available halogen relative to calcium hypochlorite.
A significant weakness of all the above inorganic compounds is their susceptibility to ultraviolet (UV) light degradation when used in an outdoor recirculating water system. As is known to the art, UV light reduces halogen levels in water, thus reducing the inorganic compounds"" ability to disinfect and sanitize. To address that weakness, the prior art has used inorganic compounds in combination with separate UV stabilizers, the best known of which is 1,3,5-triazine-2,4,6-trione (cyanuric acid), to address this weakness.
A more specific problem is associated with calcium hypochlorite. The National Fire Protection Association (NFPA) categorizes calcium hypochlorite as a Class 3 oxidizer. The NFPA code defines a Class 3 oxidizer as xe2x80x9can oxidizer that will cause a severe increase in the burning rate of combustible materials with which it comes in contact or that will undergo vigorous self-sustained decomposition due to contamination or exposure to heat,xe2x80x9d NFPA 430: Code for the Storage of Liquid and Solid Oxidizers, 1995 edition, p. 430-5.
One alternative to inorganic halogen sanitizing compounds is the class of halogenated 1,3,5-triazine-2,4,6-triones. The acid forms of halogenated 1,3,5-triazine-2,4,6-triones such as 1,3,5-trichloro-1,3,5-triazine-2,4,6-trione (trichloroisocyanuric acid) and dichloro-1,3,5-triazine-2,4,6-trione (dichloroisocyanuric acid) have high available halogen, 90% and 70% respectively. The high available halogen content and the intrinsic UV stabilizer (cyanuric acid) contained in these materials provides a cost effective, widely used sanitizing compound to treat outdoor recirculating water systems. The NFPA categorizes halogenated 1,3,5-triazine-2,4,6-triones as Class 1 oxidizers. NFPA defines Class 1 oxidizers as xe2x80x9can oxidizer whose primary hazard is that it slightly increases the burning rate but does not cause spontaneous ignition when it comes in contact with combustible materials,xe2x80x9d NFPA 430: Code for the Storage of Liquid and Solid Oxidizers, 1995 edition, p. 430-5.
However, the halogenated 1,3,5-triazine-2,4,6-triones have slow dissolution rates as a result of low solubility. This makes the halogenated 1,3,5-triazine-2,4,6-triones less desirable when rapid halogen delivery is desired. In view of this limitation, compositions like trichloroisocyanuric acid have been compressed into tablets and used in conditions where a slow or sustained release is desired. For instance, continuous or semi-continuous erosion feeding of these compositions has been effective in delivering a sanitizing amount of hypochlorous acid over a period of days as reported in U.S. Pat. No. 5,648,314 to Lachocki et al., U.S. Pat. No. 5,514,287 to Jones et al., U.S. Pat. No. 5,510,108 to Chouraqui, and U.S. Pat. No. 5,498,415 to Jones.
Other organic alternatives to the halogenated 1,3,5-triazine-2,4,6-triones for applications when rapid halogen delivery is desired are the anhydrous alkali metals salts of the acids (e.g., sodium or potassium dichloroisocyanurate). The sodium and potassium dichloroisocyanurate salts are effective sanitizers, but have reduced available halogen contents (62% and 58% respectively). Furthermore, these salts are categorized by the NFPA as Class 3 oxidizers. Sodium dichloroisocyanurate can be hydrated, reducing the NFPA oxidizer categorization to a Class 1 oxidizer, but hydrating sodium dichloroisocyanurate further reduces the available halogen contentxe2x80x94making the sanitizing compound less cost effective.
The following table compares the important characteristics of the previously described halogen sanitizing compounds.
Several attempts have been made to develop a commercially viable, rapidly dissolving, high available halogen 1,3,5-triazine-2,4,6-trione sanitizing composition. For example, Wojtowicz discloses rapid dissolving mixtures containing trichloroisocyanuric acid and alkali metal bicarbonates in U.S. Pat. No. 4,389,318. Wojtowicz also discloses rapid dissolving mixtures containing trichloroisocyanuric acid and alkaline earth metal salts of carbonate, hydroxide, oxide, and mixtures thereof in U.S. Pat. Nos. 4,472,187 and 4,498,921. In U.S. Pat. No.4,599,411, Wojtowicz discloses a mixture of trichloroisocyanuric acid, cyanuric acid, and sodium bicarbonate. However, the Wojtowicz mixtures were never commercialized.
Therefore, a need exists for stable, high dissolution rate halogenated 1,3,5-triazine-2,4,6-trione sanitizing compositions with high available halogen content. A need also exists for rapid halogen delivery sanitizing compositions that have a substantially greater half-life in the presence of UV light than inorganic halogen compositions. A need further exists for sanitizing compositions that have high amounts of available halogen in combination with other additives that provide additional benefits to recirculating water systems. The present invention addresses all of these needs.
Briefly describing one aspect of the present invention, there is provided a dry, stable, high available halogen sanitizing composition with a rapid rate of dissolution, comprising co-compacted granules of halogenated 1,3,5-triazine-2,4,6-trione and a dissolution accelerant that is an alkali metal salt of 1,3,5-triazine-2,4,6-trione.
In a further aspect of the present invention, the dissolution accelerant is replaced or supplemented by inorganic or organic disintegration agents.
In another aspect of the invention the dry, stable, high available halogen sanitizing composition further comprises additional water enhancing chemicals including: water clarifiers, flocculants, coagulants, algaestat/algaecides, and/or fungicides.
In a still further aspect of the invention, other ingredients such as dyes, surfactants, glidants, etc. may be included.
One object of the present invention is to provide a rapidly dissolving sanitizing composition of a high-available-halogen, low-solubility sanitizer, with the formulation being stable during manufacture and long-term storage.
A further object of the present invention is to provide a rapidly dissolving UV-stable sanitizing composition with a high available halogen content.
A further object of the present invention is to provide a method of applying the composition of the present invention to recirculating water.
Further aspects and advantages of the present invention will be apparent from the following description.